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Scientists Find They Are Still in the Dark Understanding How the Biggest Black Holes Were Born

11.09.2013

Current theories of supermassive black holes are incomplete, and more observational evidence is needed

Unresolved questions about the nature of supermassive black holes, gravitational monsters at the heart of nearly all large galaxies, were at the forefront of a recent conference at the Kavli Institute for Theoretical Physics (KITP) at the University of California, Santa Barbara.

Held in August, the conference, “Massive Black Holes: Birth, Growth and Impact,” brought together a diverse group of scientists from around the world to discuss how the first supermassive black holes may have formed, how they grew so fast in the early universe, and what role they played in the formation and growth of the first galaxies.

Among the topics: how theoretical predictions describing the formation and growth of these astronomical objects are failing to explain our latest astronomical observations.

“At this conference it has become clear that we are missing something when trying to explain how a black hole grows into a supermassive black hole found in the center of a galaxy,” said Priyamvada Natarajan, a professor in the Departments of Astronomy and Physics at Yale University. “For decades we’ve expected these supermassive black holes were all originally small black holes that somehow grew into these monsters at the hearts of galaxies. But our computer simulations of black hole growth, based largely on theoretical ideas, show that they prematurely stunt their own growth and fail to become the heaviest supermassive black holes that we are detecting. So our theories need to be revised.”

Natarajan remarks came at the end of the conference when she participated in a Kavli Foundation roundtable discussion with three other speakers: Andrea Merloni, a researcher at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany; Tommaso Treu, a professor in the Department of Physics at U.C. Santa Barbara; and John Wise, an assistant professor at the Center for Relativistic Astrophysics at the Georgia Institute of Technology.

According to Merloni, fundamental questions remain about even the basics about how black holes grow. “We have a theoretical understanding of how matter gets into a black hole, forming a disk around it as it does so, for example,” he said. “But we haven’t fully connected our theories to what we observe, especially with quasars, these incredibly bright centers of very distant galaxies that serve as beacons of the early universe.”

How supermassive black holes at the center of galaxy clusters interact with gas and even dark matter in the cluster is also unknown. “The most interesting (question) for me is how the outgoing energy affects the underlying distribution of dark matter,” said Treu. “We want to know because you can learn about the physical properties of dark matter – whether it interacts with itself, whether it is warm or cold, and so on. But in order to understand that, you need to understand dark matter’s relationship to black holes – how black holes and dark matter “talk” to each other.”

More from the roundtable discussion can be found at The Kavli Foundation’s website: http://www.kavlifoundation.org/science-spotlights/black-holes-revisited

LIVE GOOGLE HANGOUT: On Sept. 11 from Noon-12:30 PDT, The Kavli Foundation will host a Google Hangout on supermassive black holes with three researchers: Roger Blandford from the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, Priyamvada Natarajan from Yale University and John Wise from Georgia Tech. Details on this Hangout can be found at http://www.kavlifoundation.org/science-spotlights/spotlight-live-black-holes-cosmic-evolution

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